Printer with mounting structure for print head

Abstract

A printer having a print head with a mounting portion, and a carriage with a supporting structure engaging the mounting portion of the print head to hold it in place on the carriage. The supporting structure includes a lateral positioning portion for positioning the print head laterally in a direction of movement of the carriage, a downward positioning portion for positioning the print head downwardly of the carriage, and a rear wall for receiving a force of reaction of the print head upon printing action on a platen. The printer comprises a biasing device for biasing the mounting portion of the print head downwardly and rearwardly against the downward positioning portion and rear wall of the supporting structure of the carriage, respectively. The carriage may include a serrated portion fixedly engaging a toothed belt for driving the carriage along the platen. In this instance, the printer includes a retainer member supported by the carriage to hold a linear section of the belt in engagement with the serrated portion, and hold a flexible cable connected to the print head in pressed contact with the linear section of the toothed belt.

What is claimed is: 
     
       1. A printer having a platen for supporting a sheet of paper, a carriage movable along a length of the platen, a print head carried by the carriage to print characters on the sheet of paper along a line of printing parallel to the length of the platen, and a flexible cable connected to said print head to apply printing signals thereto, comprising: an endless toothed belt disposed so as to include a linear section movable along said line of printing to drive said carriage, said toothed belt having teeth on an inner surface thereof; and   a serrated portion formed on said carriage and fixedly engaging said teeth of said toothed belt; and   a retainer member supported by said carriage to hold said linear section of the toothed belt with its teeth in engagement with said serrated portion of the carriage,   said flexible cable being interposed between said retainer member and said linear section of said toothed belt, whereby said flexible cable and said toothed belt are held between said carriage and said retainer member,   said carriage including at least one pair of opposed projections which are spaced from each other in a direction perpendicular to the direction of movement of said carriage so as to define a gap therebetween, said gap being greater than a thickness of said toothed belt but smaller than a width of the toothed belt, said retainer member being forced by said at least one pair of opposed projections toward said serrated portion of the carriage.   
     
     
       2. The printer of claim 1, wherein said retainer member is inserted between said toothed belt and said at least one pair of opposed projections, said retainer member comprising a stopper portion abutting on said carriage to limit a distance of insertion of the retainer member, and a resilient latching hook engaging said carriage to lock the retainer member in position while the retainer member is inserted with said stopper portion abutting on the carriage, said latching member being elastically deformable in sliding contact with the carriage when the retainer member is inserted. 
     
     
       3. The printer of claim 1, wherein said carriage includes a first and a second side wall, extending upright from lateral opposite ends thereof, respectively, said at least one pair of opposed projections comprising a first pair of opposed projections formed on said first side wall, and a second pair of opposed projections formed on said second side wall. 
     
     
       4. The printer of claim 3, wherein said serrated portion of the carriage has a central recess, and said retainer member includes a presser boss for forcing a part of said toothed belt into said central recess. 
     
     
       5. The printer of claim 4, wherein said retainer member comprises an elongate portion extending along said linear section of the toothed belt, said elongate portion including a pair of notches formed in a portion thereof corresponding to said second side wall while said elongate portion is placed in a first position thereof at which a first end of the elongate portion is located inwardly of said first side wall, said pair of notches permitting said second pair of opposed projections to pass therethrough, said elongate portion being placed in said first position with said second pair of opposed projections having passed said pair of notches, said elongate portion being moved from said first position to a second position thereof at which said first end thereof is inserted between said linear section of the toothed belt and said first pair of opposed projections while the portion thereof adjacent to said pair of notches is inserted between said linear section of the toothed belt and said second pair of opposed notches, said presser boss being located opposite to said central recess while said elongate portion is placed in any positions between said first and second positions. 
     
     
       6. The printer of claim 5, wherein said elongate portion includes a stopper portion abutting on said second pair of opposed projections to limit a distance of insertion of the elongate portion from said first position to said second position, and said retainer member further comprises a resilient latching hook engaging said carriage to lock the elongate portion in said second position, said latching member being elastically deformable in sliding contact with said carriage. 
     
     
       7. The printer of claim 1, wherein said serrated portion is formed in the upper surface of said carriage, and said carriage includes a cable guide portion of inverted-L shape having a horizontal section extending substantially horizontally rearwardly from said serrated portion, and a vertical section extending downwardly from a rear end of said horizontal section, said retainer member including a cable retaining portion of inverted-L shape which cooperates with said cable guide portion of the carriage to sandwich said flexible cable therebetween, said cable retaining portion having a horizontal and a vertical section substantially parallel to said horizontal and vertical sections of said carriage, respectively. 
     
     
       8. The printer of claim 7, wherein an upper surface of said horizontal section of said cable guide portion of the carriage is higher in level than a top surface of said serrated portion of the carriage. 
     
     
       9. The printer of claim 7, wherein said vertical section of said cable retaining portion of the retainer member includes a biasing piece which is fixed at a lower end thereof to the vertical section of the cable retaining portion, said biasing piece being elastically deformed with a free end thereof in pressed contact with said flexible cable and biasing the flexible cable against said vertical section of said cable guide portion while said retainer member is placed in position. 
     
     
       10. A printer having a platen for supporting a sheet of paper, a carriage movable along a length of the platen, and a print head carried by the carriage to print characters on the sheet of paper along a line of printing parallel to the length of the platen, comprising: a supporting structure provided on said carriage, including a lateral positioning portion for positioning said print head laterally of said carriage in a direction of movement thereof along said line of printing, a first bearing section, a downward positioning portion having a second bearing section for positioning said print head downwardly of said carriage, and a rear wall for receiving a force of reaction of said print head upon printing action thereof on said platen;   a mounting portion of said print head engageable with said supporting structure of said carriage for mounting said print head in position on said carriage, said mounting portion having a rear surface contacting said rear wall of the supporting structure, and a front surface substantially parallel to said rear surface; and   a sheet spring for biasing said mounting portion of the print head rearwardly and downwardly against said rear wall and said downward positioning portion of said supporting structure, with a first and a second component of a biasing force, respectively, said sheet spring including a body portion which contacts an upper edge and a lower portion of said front surface of the mounting portion but is spaced at an intermediate part thereof from an intermediate portion of said front surface between said upper edge and said lower portion, and a bent upper end portion bent from an upper edge of said body portion rearwardly toward said rear wall of the supporting structure,   said first bearing section of said supporting structure contacting said intermediate part of said body portion of the sheet spring and holding said intermediate part in its biasing position in the proximity of said front surface of said mounting portion, to produce said first component of the biasing force of the sheet spring, said second bearing section of the supporting structure contacting a rear end of said bent upper end portion of the sheet spring and holding said rear end thereof in its biasing position, to produce said second component of said biasing force.   
     
     
       11. The printer of claim 10, wherein said mounting portion comprises a pair of ears protruding from opposite sides of said print head in opposite directions in said direction of movement of said carriage, each of said ears being engaged by said sheet spring, said supporting structure including a pair of guide grooves slidably engageable with said pair of ears to guide the ears vertically in a direction toward said downward positioning portion, and further including a pair of detent tabs engaging the bent upper end portion of said sheet spring, the body portion of said sheet spring being inserted together with said ears in said guide grooves downwardly toward said downward positioning portion of the supporting structure, the rear edge of said bent upper end portion engaging said pair of detent tabs, while said print head is held in abutting contact with said downward positioning portion, said supporting structure having front walls partially defining said guide grooves, said front walls constituting said first bearing section, and said detent tabs constituting said second bearing section. 
     
     
       12. The printer of claim 11, wherein said sheet spring includes two generally parallel arms which are connected integrally to each other at their upper portions by a connecting portion, such that the arms of the sheet spring are disposed opposite to said ears. 
     
     
       13. The printer of claim 12, wherein said arms of said sheet spring have shoulders on their opposite inner edges, said shoulders engaging a lower surface of said print head and thereby preventing an upward movement of the sheet spring relative to said print head. 
     
     
       14. The printer of claim 11, wherein said print head is a dot-matrix print head including a nose for guiding printing wires toward and away from said platen, and a wire drive for selectively actuating said printing wires, said ears extending from opposite sides of said nose.